IV.
ACTION
OF MORPHOSTATIC
SUBSTANCES
181
single inhibitory substances is only the first step in arriving at high
morphostatic effects. Only in the combination of pairs does the full
inhibitory potency of the substance appear. This search for two morphostatic substances with broad synergistic effects opens a wide field for
developmental biology and tumour biology.
C. Growth as a Phenomenon of Biochemical Integration
1. The Morphogenetic Potential of Metabolism
If it seems necessary to characterize the cell biological effect of
morphostatic substances, a biochemical characterization of the biological
effects becomes unavoidable. This is true for growth inhibition in
regenerates and in tumours. Not only is the phase specific course of
histological processes characteristic of the growth of the regenerates,
but also the changes of biochemical state during regeneration appear as
phase specific. We mention here the pattern of cathepsin distribution
(Deuchar etal, 1957; Lehmann, 1957b; Weber, 1957a; Benz, 1957), the
pattern of catalase in the tail of Xenopus (v. Hahn, 1958, 1959b) and the
pattern of unsaturated fatty acids (Hess, 1959). Furthermore we suppose
that the whole process of regeneration is carried by the integration of
different enzyme systems. The more intense the activity level of the
different systems is, the higher is the speed of regeneration and also the
higher appears the level of the total morphogenetic potential of metabolism. The morphogenetic potential in well fed larvae is high and
shows the catalase distributed in a gradient which increases steeply
towards the tail tip whereas in starving animals the catalase distribution
is nearly without a gradient. The content in unsaturated fatty acids is
high in well fed animals but low in starving animals. Also in normal
larvae the cathepsin activity shows a gradient towards the tail tip
whereas in starving animals it is high with a gradient undergoing
peculiar oscillations (Benz, 1957).
2. Protein Turnover and Morphogenetic Potential
Our own results suggest the idea that an activation of cathepsins in
regenerates which lasts an abnormally long time and at an abnormally
high level leads to a sensible depression of the morphogenetic potential.
Probably the disturbed balance between protein synthesis and degradation is involved in this phenomenon. But it seems that in Xenopus the
equilibrium in protein turnover can easily be shifted, during longer
periods, by very different conditions. For Xenopus it seems to be a
general rule that the morphogenetic potential in growing systems
depends to a high degree upon the protein turnover. This seems also to
ACTION
OF MORPHOSTATIC
SUBSTANCES
181
single inhibitory substances is only the first step in arriving at high
morphostatic effects. Only in the combination of pairs does the full
inhibitory potency of the substance appear. This search for two morphostatic substances with broad synergistic effects opens a wide field for
developmental biology and tumour biology.
C. Growth as a Phenomenon of Biochemical Integration
1. The Morphogenetic Potential of Metabolism
If it seems necessary to characterize the cell biological effect of
morphostatic substances, a biochemical characterization of the biological
effects becomes unavoidable. This is true for growth inhibition in
regenerates and in tumours. Not only is the phase specific course of
histological processes characteristic of the growth of the regenerates,
but also the changes of biochemical state during regeneration appear as
phase specific. We mention here the pattern of cathepsin distribution
(Deuchar etal, 1957; Lehmann, 1957b; Weber, 1957a; Benz, 1957), the
pattern of catalase in the tail of Xenopus (v. Hahn, 1958, 1959b) and the
pattern of unsaturated fatty acids (Hess, 1959). Furthermore we suppose
that the whole process of regeneration is carried by the integration of
different enzyme systems. The more intense the activity level of the
different systems is, the higher is the speed of regeneration and also the
higher appears the level of the total morphogenetic potential of metabolism. The morphogenetic potential in well fed larvae is high and
shows the catalase distributed in a gradient which increases steeply
towards the tail tip whereas in starving animals the catalase distribution
is nearly without a gradient. The content in unsaturated fatty acids is
high in well fed animals but low in starving animals. Also in normal
larvae the cathepsin activity shows a gradient towards the tail tip
whereas in starving animals it is high with a gradient undergoing
peculiar oscillations (Benz, 1957).
2. Protein Turnover and Morphogenetic Potential
Our own results suggest the idea that an activation of cathepsins in
regenerates which lasts an abnormally long time and at an abnormally
high level leads to a sensible depression of the morphogenetic potential.
Probably the disturbed balance between protein synthesis and degradation is involved in this phenomenon. But it seems that in Xenopus the
equilibrium in protein turnover can easily be shifted, during longer
periods, by very different conditions. For Xenopus it seems to be a
general rule that the morphogenetic potential in growing systems
depends to a high degree upon the protein turnover. This seems also to